1. Field of the Invention
This invention relates to soil fumigant compositions and more particularly to thixotropic fumigant compositions having enhanced stability and superior shelf life.
2. Description of the Prior Art
As is known, various fumigant compositions have been widely used for fumigation of space, bulk storage, and soil. However, many of the commonly-employed fumigant compositions are volatile liquids which are not normally retained on the substrate to which they are applied for significant periods of time.
It has previously been suggested that the application of such volatile fumigants be prolonged by providing them in gelled form. Dawson, U.S. Pat. No. 3,337,399, issued Aug. 22, 1967, describes the use of colloidal silica at a level of approximately two percent to approximately 10 percent by weight as a gelling agent in fumigant compositions comprising mixtures of fumigants such as methyl bromide, ethylene dibromide, carbon tetrachloride or the like.
However, one problem encountered with the gelled fumigant compositions of the U.S. Pat. No. 3,377,399 is that such compositions have serious stability and shelf life problems. Such compositions are frequently stored and dispensed from pressurized containers, and it has been found that the properties of such gelled fumigant compositions deteriorate such that they can only be dispensed and applied to the substrate in question with great difficulty. Such prior art formulations have demonstrated poor viscosity stability over time, and they also corrosively attack mild steel, the construction material frequently used for fumigant containers. Furthermore, gelled fumigant compositions produced in accordance with U.S. Pat. No. 3,337,399 frequently have been difficult to formulate because of their high initial viscosity levels.
Accordingly, it is a primary object of the present invention to provide improved, stabilized thixotropic haloaliphatic liquid hydrocarbon fumigant compositions.
Another object is to provide fumigant compositions of the character described that exhibit improved viscosity stability.
A related object is to provide gelled fumigant compositions that are easier to produce and dispense.